Superstore indirect with steam boiler

We have been using a lot of superstores with steam boilers of late with success

Question

How close to the waterline can you come with the coil height safely.

Just installed an Ssu 60 But would've much preferred to use an Ssu 80.

The supply tapping on the 80 is 29" From the floor.

Supply tapping on the 60 is 9 inches from the.

I know technically speaking I should be Able to achieve this no problem With flow control

Valves.

Have done this with radiators in the past and worked well.

But there's a big difference with one or two Rads not working and no hot water. no hot water is emergency!!!!!!!

Are there any other and indirects with the coil realy low for the larger HW demands